Using data from NASA’s New Horizons spacecraft, the Hubble Space Telescope and the ESO’s Very Large Telescope, a team of international scientists has found that Jupiter’s Little Red Spot (LRS) has some of the highest wind speeds ever detected on any planet.

Jupiter’s Little Red Spot, otherwise known by the name of Red Spot Junior, is a fierce anticyclone, a storm whose winds circulate in an anti-clockwise direction, nearly the size of the Earth and as red as the larger and more well known Great Red Spot (GRS). The evolution of the LRS began with a dramatic merger of three smaller white storms that had been observed since the 1930s – two of these storms combined forces in 1998 and subsequently merged with a third major storm in 2000. In late 2005, the giant storm curiously turned red.

"This storm is still developing, and some of the changes remain mysterious,” says Dr Andrew Cheng of the Johns Hopkins University Applied Physics Laboratory. “This unique set of observations is giving us hints about the storm's structure and makeup; from this, we expect to learn much more about how these large atmospheric disturbances form on worlds across the Solar System."

Jupiter's raging Little Red Storm. Winds whip around the LRS at speeds of up to 620 kilometres per hour. The south tropical disturbance appears in the north of the image and a small oval shaped disturbance appears in the southeast. Image: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/HST.

By observing the LRS in the infrared, scientists could “see” the thermal structure and dynamics beneath the visible cloud layers, confirming that the thermal structures and cloud features of the LRS are very similar to those of the GRS. The wind speeds of the LRS, however, were found to peak at an impressive 620 kilometres per hour, far exceeding the 250 kilometres per hour threshold that would make it a devastating Category 5 storm on Earth.

"Both the LRS and the GRS extend into the stratosphere, to far higher altitudes than for the smaller storms on Jupiter," says Dr Hal Weaver, New Horizons project scientist. The scientists think that the reddening of the two giant storms is therefore due to ferocious storm winds dredging up material from below.

The venerable Great Red Spot may soon be outgrown by its younger sibling; the LRS already rivals the steadily shrinking GRS in size and wind speed, and new thermal and wind field observations hint at an interaction between the south tropical disturbance and a warm cyclonic region south of the LRS, forming a complex that could even dwarf the Great Red Spot.

"The Great Red Spot may not always be the largest and strongest storm on Jupiter,” says Dr Glenn Orton of NASA’s Jet Propulsion Laboratory. “Continued monitoring of Jupiter's constantly evolving atmosphere will surely yield more surprises."

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